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Full text of "Text Book Of Mechanical Engineering"

928

Appendix III.

i

200 X 100 = 20,000 watts
or in one hour = 20,000 watt hours

20,000            „       ,   r r«    ,

=  —L— = 20 Board of Trade units
I000         ------------------------------

Again 2oxig  = 26*5 E.H.P. given off
and ^Q~  = 31*2 M.H.P. to drive it

P. 568. Live Rollers.—Messrs. Crandali and Martin (Am.
Soc. C.E.) experimented on rollers i inch to 4 ins. diameter, and
\\ ins. long. They found, with four crushing surfaces,

p =

where £> = -0063 for C. I. rollers
= 'oi2 for W. I. rollers
= '0073 for steel rollers

They also found the crushing load to be represented in Ibs.
by 880 x roller diameter."

580. Efficiencies in long-distance transmission of
power. — The following table has been given by Beringer,
shewing total efficiency of transformation and transmission, and,
though probably open to some correction, is the best at present
obtainable:

EFFICIENCIES PER CENT,

Distance transmitted . in miles
	Hydfaulic Power
	Com pressed Air without re-heating
	Wire Rope

\
	50
	55
	9*

I
	49
	54
	*5

3
	4*
	5i
	61

5
	37
	5o
	43

10
	26
	43
	2 1

13
	18
	39
	II